The Junkers J 3 was an all-metal single-seat experimental fighter aircraft.

Design and development

A major drawback of the previous J 1 and J 2 designs was the weight of their overall construction, which consisted of heavy iron sheets and pipes. The ''Inspektion der Fliegertruppen'' (Idflieg) saw all-metal construction as only useful for

ground attack In military tactics, close air support (CAS) is defined as air action such as air strikes by fixed or rotary-winged aircraft against hostile targets near friendly forces and require detailed integration of each air mission with fire and movement ...

and

observation aircraft A surveillance aircraft is an aircraft used for surveillance. They are operated by military forces and other government agencies in roles such as intelligence gathering This is a list of intelligence gathering disciplines. HUMINT Human ...

, being too heavy for use in fighters. In April 1916, in an attempt to prove Idflieg wrong,

Hugo Junkers Hugo Junkers (3 February 1859 – 3 February 1935) was a German aircraft engineer and aircraft designer who pioneered the design of all-metal airplanes and flying wings. His company, Junkers Flugzeug- und Motorenwerke AG (Junkers Aircraft and Mo ...

commissioned his head engineer Otto Mader in

Dessau Dessau is a town and former municipality in Germany at the confluence of the rivers Mulde and Elbe, in the '' Bundesland'' (Federal State) of Saxony-Anhalt. Since 1 July 2007, it has been part of the newly created municipality of Dessau-Roßlau ...

to develop a small, single-seat experimental aircraft of all-metal construction that could meet the climbing performance and maneuverability requirements of fighter aircraft. Junkers suggested the use of

duralumin Duralumin (also called duraluminum, duraluminium, duralum, dural(l)ium, or dural) is a trade name for one of the earliest types of age-hardenable aluminium alloys. The term is a combination of '' Dürener'' and ''aluminium''. Its use as a tra ...

, produced since 1909 at Dürener Metallwerke AG, which had been available in sufficient quantities for some time and promised a weight reduction of 60% compared to a conventional iron construction. Mader envisaged two variants of the J 3; the J 3-I single-seat fighter, and the J 3-II two-seat attack aircraft. A special feature of the construction was the use of corrugated sheets to compensate for the lower strength of the duralumin sheets. The underlying tube construction was made of duralumin, with steel at critical construction points. The aircraft was powered by a

Oberursel U.III The Gnome 7 Lambda was a French designed, seven-cylinder, air-cooled rotary aero engine that was produced under license in Britain and Germany. Powering several World War I-era aircraft types it was claimed to produce from its capacity of alt ...

rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and i ...

, which was lighter than the Mercedes D.III that powered the J 2. Also new in the design of the J 3 was the three-section wing, consisting of a center section integrated into the fuselage and a pair of outer sections. The outer sections were attached to the center section using

ball screw A ball screw (or ballscrew) is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as bein ...

s, which were a feature of later, allowing interchangeability of the outer wings. The J 3 was built using

rivet A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the ''tail''. On installation, the rivet is placed in a punched ...

s, as

welding Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing Fusion welding, fusion. Welding is distinct from lower ...

was found to be not easily applicable when using light metals. The development and construction of the prototype took place without any order from IdFlieg and was operated entirely at Junkers' own expense. In the run-up to the actual J 3 prototype construction, an airfoil made of duralumin was first produced and subjected to extensive load tests. By using duralumin instead of iron, the weight of the wing could be reduced by a third. Since the welding process used in the J 1 and J 2 was to be replaced by riveted joints in the J 3, extensive experiments were carried out in the workshop on riveting processes in advance of the actual prototype construction. Construction of the prototype J 3-I began in the summer of 1916. By autumn 1916, the entire tubular frame and the corrugated iron cladding of the wings had already been completed. However, lack of funds and the looming IdFlieg order for the

Junkers J 4 Junkers Flugzeug- und Motorenwerke AG (JFM, earlier JCO or JKO in World War I, English: Junkers Aircraft and Motor Works) more commonly Junkers , was a major German aircraft and aircraft engine manufacturer. It was founded there in Dessau, Ge ...

forced Hugo Junkers to stop work on the half-finished J 3 in October 1916. Mader and his engineers devoted themselves to the construction of the Junkers J 4 from November 1916 onwards. Duralumin was also used in the construction of the J 4, which later became the first all-metal aircraft of lightweight construction, instead of the J 3.

Legacy

Although the Junkers J 3 was not completed, it laid the decisive foundations for future light aircraft construction. The use of riveting in aircraft and fixture construction, and the basic design criteria for light metal aircraft resulted from the development of the J 3. Numerous design elements of the J 3, such as ball screw connections and corrugated sheet metal, remained defining features of Junkers aircraft from the 1920s up to the

Junkers Ju 52 The Junkers Ju 52/3m (nicknamed ''Tante Ju'' ("Aunt Ju") and ''Iron Annie'') is a transport aircraft that was designed and manufactured by German aviation company Junkers. Development of the Ju 52 commenced during 1930, headed by German Aeros ...

Variants

;J 3-I :Single-seat fighter. Prototype abandoned midway through construction. ;J 3-II :Two-seat ground attack aircraft. None built.

Survivors

The half-finished Junkers J 3 was stored in Dessau with the J 1 and several J 2s. In the mid-1920s, these aircraft were brought to an exhibition at the newly emerging Junkers Lehrschau to document the early phase of all-metal aircraft construction. Some sources report that the J 3 was destroyed in a bombing raid, while others report that the Americans removed the exhibition before Dessau was evacuated. Nevertheless, all traces of the J 3 prototype were lost towards the end of the Second World War.

Specifications (J 3-I, as designed)

References